Phenol is most commonly produced by the Hock process. The Hock process involves alkylation of benzene with propylene to produce cumene, oxidation of the cumene to the corresponding hydroperoxide, and cleavage of the hydroperoxide to produce equimolar amounts of phenol and acetone.
The various steps involved in the production of phenol and acetone from cumene can produce various contaminants that are difficult to separate from the desired phenol and acetone. These contaminants, if left in the phenol product, may cause difficulties in downstream processing, or render the phenol unusable for such downstream processing, for example, in the subsequent production of bis-phenols and polycarbonates. Therefore, techniques have been proposed to remove those contaminants involving certain treatments. For example, U.S. Pat. No. 5,064,507 discloses obtaining high purity phenol from cleavage of cumene hydroperoxide through one or more amine treatment steps. The phenol mixture includes at least 0.5 wt % to no greater than 10 wt % of alpha-methylstyrene, and further includes acetol, 2-phenyl-propionaldehyde (2PPA), methyl-benzofuran (MBF), mesityl oxide (MO) and carbonyl impurities. In addition, U.S. Pat. No. 3,322,651 discloses a method of producing phenol made by decomposition of cumene hydroperoxide. The phenol is purified by contacting the carbonyl compounds with a nitrogen compound.
Cyclohexanone is typically produced by the oxidation of cyclohexane, or the hydrogenation of phenol. These methods can also generate various contaminants that are difficult to separate from the desired product, and that can render the cyclohexanone product substandard or unusable to downstream processes, for example, in the manufacture of caprolactam or adipic acid, or further using those derivatives in the production of one or another type of nylon. Thus, certain treatment means have been described to remove those contaminants from cyclohexanone. For example, U.S. Pat. No. 7,199,271 discloses a method for reducing the concentration of cyclohexenone in a cyclohexanone-containing organic mixture. The method includes contacting an organic mixture comprising cyclohexenone with an effective amount of at least one of sulfurous acid, a salt of sulfurous acid, an alkali hydroxide, or a mixture of two or more of these compounds.
The production of phenol from cyclohexylbenzene is an emerging technology, interesting in that it co-produces cyclohexanone rather than acetone. Cyclohexylbenzene can be produced, for example, by direct alkylation of benzene with cyclohexene, or as disclosed in U.S. Pat. No. 6,037,513, by contacting benzene with hydrogen in the presence of a catalyst. The cyclohexylbenzene can then be oxidized to the corresponding hydroperoxide and the peroxide cleaved to phenol and cyclohexanone using an acidic cleavage catalyst.
The production of phenol and cyclohexanone from cyclohexylbenzene also produces various contaminants that are difficult to separate from the desired products. However, the nature of those contaminants and the separations involved are significantly different than those involved in either the conventional Hock process for phenol and acetone, or the conventional production of cyclohexanone from cyclohexane or phenol. For example, hydroalkylation of benzene produces significant amounts of inter alia, cyclohexane and lesser amounts of methylcyclopentane, cyclohexene, phenylcyclohexene, and phenylcyclohexyldiene. Similarly, the oxidation of cyclohexylbenzene typically produces peroxide species alien to the Hock process, such as the desired cyclohexyl-1-phenyl-1-hydroperoxide (CHBHP), and undesired byproduct hydroperoxides such as cyclohexyl-1-phenyl-2-hydroperoxide, cyclohexyl-1-phenyl-3-hydroperoxide and cyclohexyl-1-phenyl-4-hydroperoxide. Finally, the cleavage of these various hydroperoxides produces, as both the product of the undesired hydroperoxides and the undesired byproducts of the desired CHBHP, a wide variety of contaminant species are not produced by the chemistry and technology of either the Hock process, or the cyclohexane oxidation or phenol hydrogenation processes.
That said, described herein are methods to manage the contaminants generated when manufacturing phenol and cyclohexanone from cyclohexylbenzene, thereby forming high-quality phenol or cyclohexanone compositions.
Advantageously, the methods described herein produce cyclohexanone compositions that are novel, useful and very different from those typically produced by conventional methods (e.g., the Hock process). The chemistry associated with cyclohexylbenzene as a starting material in the instant invention, and further the complete absence of cumene and its conversion products and byproducts, potentially provides a phenol composition with contaminants that are of a markedly different type and concentration than the conventional methods. These contaminants may be less problematic in further processing, e.g., to caprolactam, and/or because of their lower volatility compared to conventional methods, they may be present in lower concentrations.